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UPSC Geography Notes – Soils of India: Types, Distribution, Crops & Conservation

 

UPSC Prelims Notes – Soils of India


1. Importance of Soil

  • Soil is a dynamic natural body consisting of minerals, organic matter, water, air, and living organisms.

  • It is one of the most important natural resources because:

    • Provides nutrients and water for plant growth.

    • Supports agriculture → ensures food security.

    • Acts as habitat for microbes, insects, worms.

    • Regulates water cycle and carbon cycle.

    • Prevents floods and erosion.

  • Soil diversity in India leads to diverse cropping patterns.

2. Soil Formation (Pedogenesis)

Soil forms through weathering of rocks.

Types of Weathering

  • Physical weathering → Temperature change, wind, water, glaciers.

  • Chemical weathering → Oxidation, hydration, carbonation.

  • Biological weathering → Roots, microbes, animals.

Factors Affecting Soil Formation

  1. Parent rock material

  2. Climate (rainfall & temperature)

  3. Relief/topography

  4. Vegetation

  5. Time

Example: Basalt rocks → Black soil.

3. Soil Profile & Horizons

Soil layers are called Horizons.

A Horizon (Topsoil)

  • Dark due to humus.

  • Rich in nutrients and minerals.

  • Supports plant roots and organisms.

  • Most fertile layer.

B Horizon (Subsoil)

  • Accumulation of minerals like iron, clay.

  • Less humus.

  • Hard and compact.

C Horizon

  • Weathered parent rock material.

  • Loose rock fragments.

Below → Bedrock (Parent rock).

Term: Vertical arrangement of horizons = Soil Profile.

4. Soil Classification

A. Based on Particle Size

1. Sandy Soil

  • Large particles.

  • Low water retention.

  • Good aeration.

  • Poor fertility.

2. Clayey Soil

  • Very fine particles.

  • High water retention.

  • Poor aeration.

  • Sticky when wet.

3. Loamy Soil

  • Mix of sand + clay + silt.

  • Best for agriculture.

  • Balanced moisture and nutrients.

B. Major Soil Types of India (ICAR Classification)

  1. Alluvial Soil

  2. Black Soil

  3. Red & Yellow Soil

  4. Laterite Soil

  5. Arid Soil

  6. Saline Soil

  7. Peaty Soil

  8. Forest Soil

5. Major Soil Types in India – Detailed Notes

1. Alluvial Soil

  • Formed by deposition of rivers.

  • Covers about 40% of India’s area.

  • Found in:

    • Northern Plains

    • Brahmaputra valley

    • River deltas (Mahanadi, Godavari, Krishna, Kaveri)

    • Coastal plains

Types

  • Khadar → New alluvium; very fertile; floodplains.

  • Bhangar → Old alluvium; less fertile; uplands.

Features

  • Texture varies from sandy to clayey.

  • Light grey colour.

  • Rich in potash and lime.

  • Poor in nitrogen and phosphorus.

Crops

Rice, wheat, sugarcane, cotton, pulses, oilseeds.



4

2. Black Soil (Regur Soil)

  • Derived from basalt rocks.

  • Found in Deccan Plateau:
    Maharashtra, MP, Gujarat, Telangana, TN.

Features

  • Clayey and deep.

  • High moisture retention.

  • Develops cracks in summer → self-ploughing.

  • Sticky when wet.

Nutrients

  • Rich in lime, iron, magnesium.

  • Poor in nitrogen and phosphorus.

Crops

Cotton (most important), sugarcane, wheat, sunflower.


4

3. Red & Yellow Soil

  • Developed on crystalline igneous rocks.

  • Found in:
    Tamil Nadu, Karnataka, AP, Odisha, Chhattisgarh.

Colour

  • Red due to iron oxide.

  • Yellow when hydrated iron present.

Features

  • Porous and friable.

  • Low fertility.

Nutrients

  • Poor in nitrogen, phosphorus, humus.

Crops

Millets, pulses, groundnut, potato, fruits.



4. Laterite Soil

  • Formed under high rainfall & temperature.

  • Found in:
    Kerala, Karnataka, TN, Odisha, Assam hills.

Formation

Heavy leaching removes silica → leaves iron & aluminium.

Features

  • Poor fertility.

  • Hard when dry.

  • Used to make bricks.

Crops

Tea, coffee, rubber, coconut, cashew.

4

5. Arid Soil

  • Found in Western Rajasthan & Gujarat.

Features

  • Sandy texture.

  • Saline nature.

  • Low humus.

Crops

Millets, barley with irrigation.

6. Saline Soil

  • Also called Usar soil.

Causes

  • Poor drainage.

  • Excess irrigation.

  • Sea water intrusion.

Found in

Punjab, Haryana, Rajasthan, Gujarat, Sundarbans.

Treatment

  • Gypsum.

  • Drainage.

  • Salt-tolerant crops.

7. Peaty Soil

  • Found in Bihar, West Bengal, Odisha, TN coasts.

Features

  • Very high organic matter.

  • Black colour.

  • Acidic and heavy.

8. Forest Soil

  • Found in Himalayas and hill forests.

Features

  • Coarse on slopes.

  • Loamy in valleys.

  • Acidic in cold areas.

Crops

Tea, coffee, spices, fruits.

6. Soil Nutrient Deficiency

Major Nutrients

  • Nitrogen

  • Phosphorus

  • Potassium

Micronutrients

  • Zinc

  • Iron

  • Copper

Effects

  • Poor crop yield

  • Weak plants

Solutions

  • Crop rotation

  • Green manure

  • Organic farming

  • Fertilisers

7. Soil Degradation

Causes

  • Deforestation

  • Overgrazing

  • Mining

  • Excess fertilisers

  • Urbanisation

  • Soil erosion

Types

  • Water erosion

  • Wind erosion

  • Salinisation

  • Desertification

8. Soil Conservation Methods

  • Contour ploughing

  • Terrace farming

  • Strip cropping

  • Shelter belts

  • Check dams

  • Afforestation

  • Controlled grazing

9. Important Institutions

  • Soil Survey of India – 1956.

  • NBSS & LUP – Under ICAR.

  • Conduct soil mapping and research.

10. Prelims Special One-Line Facts

  • Black soil = Regur soil.

  • Laterite soil → Brick making.

  • Khadar = New alluvium.

  • Bhangar = Old alluvium.

  • Red soil colour → Iron oxide.

  • Arid soil → Western Rajasthan.

  • Saline soil → Usar soil.

  • Peaty soil → High organic matter.

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